In the second trial, the vacuum removed air resistance from the equation, allowing both objects to be affected only by gravity. Acceleration due to gravity is constant, regardless of the mass of the object.

Brian Cox, a particle physicist at the University of Manchester, decided to scale up the experiment just a smidgen. On an episode of Human Universe, Cox ventures to NASA's Space Power Facility in Cleveland, Ohio in order to replicate the experiment with a bowling ball and large feathers.

The facility was designed to replicate the vacuum of space, in order to test out spacecraft during development. In the video, however, it's used to test out one of the most fundamental forces of the Universe.

It is generally believed that Galileo first had the idea that gravity was a constant force in 1589 when he dropped a cannonball and musketball from the top of the Leaning Tower of Pisa in Italy. Though the two objects had greatly different masses, they hit the ground at the same time. Modern incarnations of the experiment use a feather to demonstrate the effect of air resistance, and help show the true effect of gravity.